The value of loyalty is on the decline if you are an airline passenger.

When United and Delta Air Lines announced plans recently to overhaul their loyalty rewards programs, industry experts assumed the changes would benefit airlines at the expense of passengers.

Now a new study calculates exactly how much fliers will lose.

Both airlines announced plans to switch from a loyalty rewards program that awards miles based on total distance flown to programs that dole out miles based on how much travelers spend on air fare.

Members of United’s MileagePlus program will collect an average of 11% fewer reward miles, flying on the most popular routes, under changes that take effect March 1, according to a study by Boston flight research site Hopper.com.

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The nation's largest airlines continue to rate low in customer satisfaction -- an average of only 69 on a scale of 1 to 100 points. Customer satisfaction with airlines ranks below satisfaction with insurance companies, fast food restaurants, utility companies and banks. Among the nation's largest air carriers, New York-based JetBlue scored highest for the third year in a row. But the satisfaction rating for four of the six largest airlines dropped in 2014 compared with the previous year. Even JetBlue's rating dropped. The rating by the American Customer Satisfaction Index found that the in-flight experience, especially seat comfort, has pulled the overall scores down. -- Hugo Martin (American Customer Satisfaction Index)

Meanwhile, members of Delta’s Skymiles program will get an average of 22% fewer miles under changes starting Jan. 1, the study said.

The impact on individual fliers will vary, depending on the loyalty tier of the traveler and the fares they pay.

Among major air carriers, only American Airlines continues to offer a distance-based loyalty system. Brian Kelly, a loyalty rewards expert and founder of the website Thepointsguy.com, said American may leave its program unchanged to differentiate itself from competitors.

“I don’t think its a slam dunk that American will follow,” he said.

To read more about travel, tourism and the airline industry, follow me on Twitter at @hugomartin.